Camshaft phasers are used in combustion engines to vary the valve timing of the combustion chamber valves. Consumption and emissions are reduced by adapting the valve timing to the actual load. One common type is the vane-type adjuster. Vane-type adjusters have a stator, a rotor and a drive sprocket. For the most part, the rotor is connected to the camshaft for conjoint rotation therewith. The stator and the drive sprocket are likewise interconnected, the rotor being disposed coaxially to and within the stator. The rotor and the stator have radial vanes that form oil chambers (vane cells) that act in mutual opposition and can be pressurized by oil and allow a relative movement between the stator and rotor. In addition, the vane-type adjusters have various sealing covers. A plurality of screw connections ensure a secure interconnection of the stator, drive sprocket and sealing cover.
U.S. Patent Application 2009/0173297 A1 describes a hydraulically actuable camshaft phaser that has a drive sprocket and, coaxially thereto, a stator having two rotors disposed concentrically relative to the stator. The stator can be made in one piece or be composed of a plurality of components. The rotors and the stator have radially oriented vanes. Thus, the stator and the rotors form working chambers that can be supplied with a hydraulic pressure medium, producing a relative rotation about the axis of rotation of the camshaft phaser between the rotor and the stator in question. A partitioning wall, which, as a component of the stator, is disposed between the rotors, axially separates the rotors from one another. Each rotor can be attached to a camshaft. In such a case, the camshaft is formed as a hollow shaft, while the other camshaft is made of solid material. The two camshafts are disposed mutually concentrically. The cams assigned to the associated camshafts are joined to the respective camshaft thereof to permit a circumferential rotation of the cams, and/or of the respective camshafts relative to one another, so that the valve timing of the intake and exhaust valves assigned to the cams is infinitely and variably adjustable.
The vanes of the rotors and those of the stator have a specific surface area, which, upon filling of the working chambers with a hydraulic medium, are subject to a pressure and thus to a circumferential force, resulting in the relative rotation. The response characteristic of such a hydraulic camshaft phaser is determined by this surface area and by the hydraulic medium pressure generated by a pressure medium pump.